Silberbaum (chemistry)

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A silver tree (tree of Diana, Dianenbaum, Latin Arbor Dianae , or Philosophenbaum, Latin arbor philosophica ) consists of tree-like crystals of silver or silver amalgam . It occurs when silver is deposited by reduction from a silver salt solution. Above all, the mercury -containing trees created with mercury from silver nitrate solution were named after an alchemical name for silver, Diana, also Diana tree, Latin Arbor Dianae . Tree-like structures are also called dendritic , and similar metal trees can also be obtained with other metals. Sometimes spherical precipitations develop on the branches, which have been interpreted as the "fruits of the tree".

Because of its similarity to plant growth, in the 18th century the silver tree was considered to be “one of the phenomena of chemistry that is worth seeing and investigating,” which chemical philosophers - including Isaac Newton - interpreted as evidence of a kind of life in the mineral kingdom.

Historical

Silver trees that have grown on a copper coil that has been immersed in 0.1 M silver nitrate solution. Recorded after a reaction time of two hours.
Detail from a picture with silver trees on a copper coil. The picture has been rotated so that the tree that has grown down is facing up.

The history of the discovery of the Arbor Dianae is not exactly known. The first scientific evidence comes from the late 16th century by the Italian scholar Giambattista della Porta .

Other well-known descriptions of how to make silver trees include those that the natural scientist Wilhelm Homberg communicated to the Royal Academy of Sciences in Paris in 1692, and those of the French chemist Nicolas Lémery in his textbook published from 1675, which was published from 1698 under the title “ The perfect chymist ”also appeared in German. In 1710, Wilhelm Homberg presented his procedure as follows:

"Make a cold amalgama out of four quarts of silver files or silver leaves, and two quints of mercury, dissolve this amalgama in a sufficient amount (about 4 ounces) of pure and moderately strong saltpeter spirit, dilute the solution with about 1½ pounds of distilled water, shake it up Mixture and save in a stoppered glass bottle. If you want to use this preparation, you take an ounce of it, pour it into a vial , add gold or silver amalgama, the size of a pea, which is as soft as butter, and let the vessel stand still. You can almost immediately see threads emerging from the amalgama, which rapidly enlarge, send out branches on all sides and take on the shape of small shrubs. "

The Homberg production method was heavily criticized by Joseph Louis Proust :

"Homberg and Beaumé, with their spheres of amalgam and their dissolutions, only entangled the matter and spoiled it for those who wanted to enjoy one of the most pleasant phenomena in experimental chemistry without so many fuss."

Proust is probably referring primarily to the additional steps involved in making the silver amalgam, for which pieces of silver were first broken up by filing; From today's perspective, the interpretation of chemical processes is more difficult if one does not start from pure substances. Lémery described his procedure as follows:

"§ 2. Take an ounce of silver / let it dissolve in 2. or 3. Untzen Spiritus Nitri / bring the dissolution into a sand fire for evaporation / leave it inside / until about half of the moisture has been consumed / what remains / put in a matras , in which you put 20. Untzen common clear water / put 10 ounces of mercury underneath / put the matras in a small straw basket / and let it stand undisturbed for 40th days / you will see / how such a time is Kind of a tree with branches and small balls / which should / will form the fruits at the end.
§3. This operation has no use in the Arzeney art / I have described its only pleasing to lovers of all kinds of arts. "

Because of the long wait, this method is considered "very time consuming" (exceedingly time-consuming) .

The French researcher Charles Marie de La Condamine published from 1731 that silver trees can also be obtained from silver solutions without mercury by using other metals such as iron , copper , zinc , lead , tin or bismuth , but also brass or the semi-metal antimony can be used for this.

Modern demonstration

While mercury was often used for earlier experiments, the easiest way to demonstrate the formation of silver trees today is by reduction with copper. In the course of the experiment, the solution increasingly takes on the pale blue color of copper salt solutions. A section of a silver growth obtained in this way is shown in the picture.

During this redox reaction , part of the copper is oxidized and goes into solution, silver is reduced :

.

Silver trees can also be grown by the electrolytic decomposition of silver nitrate.

Shape of sapling

The shape of the trees is created by the accumulation of silver, which moves through the solution in the form of silver ions. Since this diffusion has a random component, the shape of the trees - especially natural if impurities or asymmetrical boundary conditions play a role - is not strictly symmetrical and the branches do not appear strictly periodic, which increases the "natural" impression of the trees. The description of the growth mechanism can be done with the model of diffusion-limited growth , in which fractal structures arise. Correspondingly, a self-resemblance can also occur if one looks at the little trees with different magnifications.

Dendritic silver in research

Compared to solid silver, dendritic silver has a much larger relative surface area. Since large surfaces can be very useful for some applications, for example in catalysis , intensive research has been carried out in recent years on the production of dendritic silver and various possible uses for it.

Literature and individual references

  1. ^ A b Ludwig Julius Friedrich Höpfner: German Encyclopedia or General Real Dictionary of All Arts and Sciences . Varrentrapp Sohn and Wenner, Frankfurt am Main 1778, p. 713 (keyword Arbor Diana).
  2. ↑ Jane Bosveld: Isaac Newton, World's Most Famous Alchemist . (English, discovermagazine.com [accessed September 8, 2013] Discover Magazine July / August 2010).
  3. ^ Robert Collis: Alchemical Interest at the Petrine Court . Turku University , (iii) Alchemy and Peter the Great, footnote [22] (English, esoteric.msu.edu [accessed September 8, 2013]).
  4. ^ Jaime Solá de los Santos, José Luis Hernández Pérez, Ricardo Fernández Cruz: Árboles químicos I: el árbol de Diana . (Spanish, heurema.com [PDF; 643 kB ; accessed on September 8, 2013]). Or Árboles químicos I: el árbol de Diana (Arbor Dianae) on heurema.com (Spanish).
  5. ↑ Nicolas Lemery: Cours de Chymie, Contenant la Maniere de Faire les Operations ... the author, Paris 1675, p. 68-77 ( digitized on Gallica [accessed September 8, 2013]).
  6. ↑ a b Nicolas Lemery: Cours de Chymie, or: The perfect Chymist, Which The ones commonly used in medicine ... Johann Jacob Winckler, Dresden 1698, p. 149–153 , urn : nbn: de: hbz: 061: 2-18093 (complete works on the part of the University of Düsseldorf).
  7. ^ Johann Samuel Traugott Gehler (Hrsg.): Physical dictionary . Attempt to explain the noblest concepts and artificial words in natural science with brief messages about the history of the inventions and descriptions of tools. 1 from A to Epo. Schwickert, Leipzig 1787, keyword "Dianenbaum, Silberbaum", p. 578-579 , p. 578 with the keyword “Dianenbaum” ( online at ECHO of the MPG I , online at ECHO of the MPG II [accessed on May 2, 2020] Copyright: Max Planck Institute for the History of Science, Max Planck Society for the Promotion of Science eV, ECHO - Cultural Heritage Online).
  8. ^ Joseph Louis Proust: Facts on the history of silver - Proust's observations on silver . In: Adolph Ferdinand Gehlen (Hrsg.): Journal for chemistry and physics . tape 1 , third issue. Publishers of the Realschulbuchhandlung, Berlin 1806, 15. Contributions to the chemistry of metals, p. 517 ( limited preview in Google Book Search or archive.org [accessed September 7, 2013]).
  9. ^ Charles Marie de La Condamine: Sur une nouvelle espèce de végétation métallique . In: Académie des Sciences de Paris (ed.): Histoire de l'Académie royale des sciences. Avec les Mémoires de Mathématique & de Physique . 1731, ISSN  1967-4783 , Chimie, p. 31–34 (French, digitized on Gallica [PDF; accessed September 7, 2013]).
  10. ↑ Johann Georg Krünitz (Ed.): Johann Georg Krünitz 'economic-technological encyclopedia or general system of state, town, house and agriculture . tape 154 . Paulische Buchhandlung, Berlin 1831, p. 217–222 ( limited preview in Google Book Search [accessed on September 7, 2013] keyword Silberbaum).
  11. ^ Walter M. Wagner: Silberbäumchen. Effect experiments, videos, petri dish experiments . Bayreuth ( daten.didaktikchemie.uni-bayreuth.de [accessed on September 7, 2013]).
  12. ↑ Fractal silver. Chemical demonstration tests . ( stromberg-gymnasium.de [accessed on September 7, 2013] picture of the experimental setup and picture of a silver tree obtained in 30 seconds).
  13. ^ Hansruedi Felix: Proposal for a Christmas performance . In: c + b - chemistry + biology . VSN trade journal. tape 05 , no. 04 . Gebr. Aeschbacher AG, Worb December 2005, 2.8. Fractal structures made of silver, p. 22 ( swisseduc.ch [PDF; 1.7 MB ; accessed on September 7, 2013]).
  14. ↑ XK Meng, SC Tang, S. Vongehr: A Review on Diverse Silver Nanostructures. Invited Review . In: Journal of Materials Science & Technology . tape 26 , no. 6 . Elsevier, June 2010, pp. 487-522 ( jmst.org [accessed September 7, 2013]).

Web links

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